Plate Tectonics

Plate tectonics

The theory of plate tectonics revolutionized the earth sciences by explaining how the movement of geologic plates causes mountain building, volcanoes, and earthquakes.

The theory of plate tectonics first formed in the beginning of the 1915s.
It started when Alfred Wegener proposed a theory of a “continental drift”
His theory was that Wegener proposed that the continents plowed through crust of ocean basis
Wegener was one of the first to realize that the Earth’s surface has changed over time and that the continents that are seperated, may have been joined together in the past
Wegener’s idea about the continental drift was controversial because there was no explanation to prove his theories at the time
Years later, Wegener’s theory was disproved
Due to the rejection of Wegener’s theory, the idea of crustal movement was first introduced to the scientific community

Born November 1st , 1880, in Berlin Germany ( Died in November 1930- Greenland )
German meteorologist and geophysicist who formulated the first complete statement of the continental drift hypothesis
Earned a Ph.D. degree in astronomy from the university of Berlin in 1905
Wegener first presented his theory in lectures in 1912
Published his most important work in 1915 called Die Entstehung der Kontinente und Ozeane (The origin of continents and oceans)
By 1930 his theory had been rejected by many geologists
Was resurrected as part of the theory of plate tectonics in the 1960s

Spreading boundaries
New oceanic crust is created from magma derived from partial melting of the mantle caused by the decompression as hot mantle rock from depth is moved toward the surface
Magma from the mantle pushing up to fill the voids left by divergence of the two plates
Pillow lavas forming where magma is pushed out into seawater
Vertical sheeted dykes intruding into cracks resulting from the spreading
Magma cooling more slowly in the lower part of the new crust and forming gabbro bodies
Spreading is hypothesized to start with a continental area with up warming or doming related to an underlying mantle plums

Two plates are moving towards each other
There are three types depending on the crust present on either side of boundary, consists of

Collision between two plates (oceanic crust and lithospheric mantle) and is pushed or subducted under the other
Common to be a trench along the boundary
The denser plate will end up sinking below the less dense plate

Occurs when a tectonic plate primarily composed of oceanic lithosphere collides with a plate with continental lithosphere
The oceanic plate is pushed under the continental plate in the same manner as at an ocean - ocean boundary
The plate with oceanic lithosphere will curve beneath the continental plate
Examples:

Occurs when a continent or large island that has been moved along with subducting oceanic crust collides with another continent
Results when two continents collide
Examples:

Two plates slide past one another
Majority of transform faults are located in the ocean basin and connects offset in the mid ocean ridges
A few connect mid ocean ridges and subduction zones
The crust of lithosphere is neither created nor destroyed
One of the most famous transform plate boundaries occurs at the San Andreas fault zone